Temporary marking is desirable in many instances, but removing the marking can be difficult and costly, or at least annoying. For example, temporary marking is desirable for price marking products for retail sale so that the price can be changed by the retailer or the purchaser can remove the price before giving the product to a recipient. To change the price on a product, a retailer often has to remove the existing price tag o. label and replace it with a new one or place a new price label over the existing marking. When a price marking is removed by a customer, substantially the entire label or tag must be removed which can involve scrapping off the adhesive label or cutting off the tag. Accordingly, there is a need for a temporary price marking which can be easily removed and replaced or changed.
Another example for the need for temporary marking is in the communication of concealed information such as the win/loss status on gaming tickets. Gaming tickets typically comprise a cardboard or paper substrate printed with the win/loss status and a layer of metalized, opaque overprinting covering the printed win/loss status. The player, after purchasing the ticket, must remove the metalized coating by scraping the metalized coating with a coin or the like to reveal the status. This is an inconvenient and messy process. Thus, there is a need for opaque temporary marking for concealing information printed on documents such as gaming tickets.
Still another example of the need for temporary printing is in the marking of terrain and structures such as roadways, signs, sidewalks, trees, and buildings, to provide a variety of messages such as hazard warnings and directions. Such markings are typically made with paint or chalk directly on the surface of the terrain or structure or by painted signs mounted on or near the terrain or structure. Changing or removing the marking requires either removing the sign or removing the direct marking by washing, abrasion, or chemical attack. These conventional methods of temporary marking are costly and inconvenient and can damage the marked substrate. Thus, there is a need for a more convenient and less destructive means of temporarily marking terrain and structures.
Yet another example of the need for temporary printing is in the underlining or highlighting of text in books or other publications. This task is typically performed with conventional markers such as pens, pencils, highlighters, and felt tip markers. However, these types of markings are not easily removed, and in many cases cannot be removed without damaging the substrate. Thus, there is a need for easily removable marking for underlining or highlighting text.
There is also a desire for a means for indicating exposure to ultraviolet radiation which can be hazardous to humans. More particularly, ultraviolet radiation can cause permanent damage to the eyes and skin. For example, arc welders must wear protective gear to prevent exposure to the ultraviolet radiation emitted during arc welding. Accordingly, there is a need for an inexpensive and convenient means for indicating the degree of exposure to ultraviolet radiation.
In addition, there is a need for improved methods for printing articles, particularly printing multicolor images on plastic articles, plastic films, and paper. Conventional methods of printing color images include photography and xerography, both of which are effective, yet problems remain with each method. Photographic printing involves a developing process which is time consuming, costly, and often includes the use or generation of undesirable chemicals. Color xerography, on the other hand, involves the use of multiple toners to produce overlapping color images. It is often difficult to accurately place the individual color images relative to one another and the result is an image that lacks sharpness. Furthermore, contoured and glossy plastic surfaces are not amenable to conventional methods of marking such as labeling, contact or direct printing, and xerography.